Method and electrochemical device for low environmental impact lithium recovery from aqueous solutions

ABSTRACT

An efficient and low environmental impact method is disclosed for the recovery of lithium from aqueous solution, for example, brines from high altitude salt lakes. The method comprises the use of an electrochemical reactor with electrodes which are highly selective for lithium, where lithium ions are inserted in the crystal structure of manganese oxide in the cathode, and extracted from the crystal structure of manganese oxide in the anode. Also disclosed are three-dimensional carbon electrodes embedded in manganese oxides formed by impregnating a porous support, for example a carbon felt, with a manganese oxide/carbon black slurry.

BACKGROUND OF THE INVENTION

The industrial importance of lithium either in the metallic form or as achemical compound is rapidly increasing due to its multiple applicationin diverse fields such as batteries, pharmacological preparations (e.g.,to treat manic depression), coolants, aluminum smelting, ceramics,enamels and glasses, nuclear fuels, or the production of electronicgrade crystals of lithium niobate, tantalite and fluoride. Lithiumcompounds are required for the fabrication of several components inlithium-air and lithium-ion batteries for electric and hybrid electricvehicles, such as the cathode materials and electrolyte salts. Somebatteries require highly pure lithium metal.

In the case of lithium-ion batteries, lithium compounds can be requiredfor the fabrication of the cathode. Lithium compounds such as lithiummanganese oxide, lithium iron phosphate, or mixed metal oxides such aslithium cobalt nickel manganese oxide can be used as active materialsfor cathodes.

Lithium compounds, e.g., lithium chloride or lithium carbonate, aretypically produced by extraction from lithium-containing minerals suchas spodumene (lithium aluminum silicate) through traditional mining orby extraction from lithium-containing brines, such as those found inhigh altitude salt lakes such as the Salar de Atacama in Chile, Salar deUyuni in Bolivia, Salar de Ollaroz, or Salar del Hombre Muerto inArgentina. Alternative brine sources, such as, geothermal, oilfield, andrelict hydrothermal brines are also promising sources for lithiumextraction.

The current commercial method for extraction and purification of lithiumfrom high altitude lakes relies on an evaporitic process of fractionalrecrystallization of chlorides of lithium, sodium, potassium, magnesium,etc. In this process, deposits containing lithium are dissolved in wateror recovered as brines, evaporated in open ponds to concentrate thesalts, and lithium is precipitated as lithium carbonate by the additionof soda ash. Subsequently, the lithium-depleted brine is discarded. Thechemical process is relatively simple, however, it has a highenvironmental impact since it takes place in high altitude salt lakes(over 4,000 meters above sea level), were water is scarce and ecosystemsare fragile. This extraction process profoundly alters the water balancein the high altitude salt lake, introduces chemicals in the environment,and generates large volumes of chemical waste. For example, theevaporation and concentration of brines under the effect of solar energyin a very slow process in which for every metric ton of lithiumcarbonate produced, at least a million liters (220,000 US gallons) ofwater are lost by evaporation at high altitude in desert regions.

The lithium reserves on land, mainly from brines, are about 14 milliontons. There is interest in developing alternative reserves to meetgrowing demand. In seawater, lithium reserves are estimated at about 230million tons, although lithium is present in much lower concentrationsthan in the brines from salt flats (0.1-0.2 ppm) and therefore it ismuch more expensive to extract. See, e.g., Abe & Chitrakar,Hydrometallurgy 19:117-128 (1987); Chitrakar et al., Ind. Eng. Chem.Res. 40:2054-2058, (2001); Kaneko & Takahashi, Colloids and Surfaces47:69-79 (1990); Kitajou, Ars Separatoria Acta 2:97-106 (2003); Kunugitaet al., Kagaku Kogaku Ronbunshu 16:1045-1052 (1990); Miyai et al.,Separation Science and Technology 23:179-191 (1988); Ooi et al.,Separation Science and Technology 4:270-281 (1986); Dang and Steinberg,Energy 3:325-336 (1978); Ryabtsev et al., Russian Journal of AppliedChemistry 75:1069-1074 (2002).

Therefore, there is a need for methods and devices to extract lithiumefficiently and economically from brines and from low concentrationsources while having a reduced impact on the environment.

BRIEF SUMMARY

The present disclosure provides an efficient and low environmentalimpact method for the recovery of lithium from aqueous solutions, forexample, brines from high altitude salt lakes. More particularly, thedisclosed method comprises the use of an electrochemical device withelectrodes which are highly selective for lithium. Lithium ions areinserted in the crystal structure of a battery-type lithium insertionelectrode (e.g., a manganese oxide) functioning as cathode in anextraction step in which the electrolyte is a brine or other aqueoussolution containing lithium. The insertion lithium is then extractedfrom the crystal structure of manganese oxide in an extraction orconcentration step it which the battery-type lithium insertion electrodefunctions as the anode and the electrolyte is a diluted aqueoussolution.

Also disclosed are electrochemical devices comprising three-dimensionalelectrodes composed of a porous substrate (e.g., a carbon felt) embeddedin a lithium insertion compound (e.g., a manganese oxide), and theassembly of multiple electrochemical devices to form an electrochemicalreactor. In some aspects, the disclosed battery-type electrodes areformed by impregnating a porous support, for example a carbon felt orcalcined coke carbon particles, with a lithium-manganese oxide/carbonblack slurry, and subsequently delithiating the lithium-manganese oxideelectrolytically.

The present disclosure provides a packed bed electrochemical cell forextracting lithium from an aqueous solution containing lithium ionscomprising:

-   -   (a) a first electrode comprising a compartment packed with a        high surface carbon substrate coated with a lithium insertion        compound comprising LiMn₂O₄,    -   (b) a second electrode comprising a compartment packed with a        high surface carbon substrate coated with a chloride reversible        electrode material; and    -   (c) a non-membranous porous material interposed between the        first and second electrode,    -   wherein the high surface carbon substrate comprises calcined        coke carbon particles.

In some aspects, the calcined coke carbon particles are calcinedpetroleum coke carbon particles. In some aspects, the chloridereversible electrode material comprises polypyrrole. In some aspects,the non-membranous porous material separating the first and secondelectrode comprises a porous fritted glass separator. In some aspects,packed bed electrochemical cell further comprises current collectioncontacts which are in contact with the electrodes. In some aspects, thecurrent collection contacts are titanium mesh current collectors.

The present disclosure also provides a packed bed electrochemical cellreactor comprising at least two packed bed electrochemical cells.

The present disclosure also provides an electrochemical method forextracting lithium from an aqueous solution containing lithium ionscomprising:

-   -   (a) contacting two electrodes with an aqueous solution        containing lithium ions, wherein the electrodes are a        battery-type electrode, and a chloride or polypyrrole reversible        electrode;    -   (b) applying a voltage or circulating a current between the two        electrodes, wherein the lithium ions are captured by the        battery-type electrode; and,    -   (c) exchanging the aqueous solution containing lithium ions with        a dilute solution of lithium chloride (or a dilute solution of        potassium chloride) and reversing the electrical polarity,    -   wherein the reversal of polarity releases lithium ions from the        battery-type electrode into the dilute solution.

In some aspects, the above disclosed method further comprises repeatingsteps (a)-(c) at least twice using the aqueous solution containinglithium ions resulting from the previous step (c) as the aqueoussolution containing lithium ions of the subsequent step (a) wherein theaqueous solution from each successive step (c) is used as the aqueoussolution containing lithium ions of the next step (a). In some aspects,steps (a)-(c) are repeated at least three times, wherein the aqueoussolution from each successive step (c) is used as the aqueous solutioncontaining lithium ions of the next step (a).

In some aspects, the aqueous solution is selected from the groupconsisting of sea water, lake water, underground water, hot-springswater, geothermal brine, oilfield brine, relict hydrothermal brine, orhigh altitude salt lake brine. In specific aspects, the aqueous solutionis sea water. In other specific aspects, the aqueous solution is ahigh-altitude salt lake brine. In some aspects, the aqueous solutioncomprises lithium ions and contaminant non-lithium metal ions. In someaspects, the battery-type electrode is a lithium insertion battery-typeelectrode comprising a porous or high surface substrate and a lithiuminsertion compound. In some aspects, the substrate is a carbonsubstrate. In other aspects, the carbon substrate is a conductivesubstrate. In some aspects, the battery-type electrode comprises aconductive additive material. In certain aspects, the conductiveadditive material is carbon black. In some aspects, the lithiuminsertion compound comprises a manganese oxide. In some aspects, themanganese oxide comprises γ-MnO₂ and/or λ-MnO₂. In some aspects, themanganese oxide has a spinel crystal structure. In certain aspects, themanganese oxide comprises LiMn₂O₄. In other aspects, the lithiuminsertion compound comprises lithium cobalt oxide, lithium ironphosphate, lithium manganese oxide, or combinations thereof. In someaspects, the lithium cobalt oxide comprises LiCoO₂. In other aspects,the lithium iron phosphate comprises LiFePO₄. In some aspects, thebattery-type electrode is prepared by electrolytical delithiation of aporous or high surface substrate coated with lithium cobalt oxide(LiCoO₂), lithium iron phosphate (LiFePO₄), lithium manganese oxide(LiMn₂O₄), or combinations thereof. In some aspects, the carbonsubstrate is selected from the group consisting of carbon felt, carboncloth, carbon paper, graphite granules, granite foam, high surface areagraphite fiber, and combinations thereof. In some aspects, the carbonsubstrate is a carbon felt. In some aspects, the carbon substrate is acalcined coke carbon substrate. In some aspects, the chloride reversibleelectrode comprises a porous or high surface carbon substrate and silvermetal particles. In other aspects, the silver metal particles arenanoparticles. In some aspects, the chloride reversible electrodecomprises an electrically conductive polymer. In other aspects, theelectrically conductive polymer is a polypyrrole. In some aspects, thelithium ions in the aqueous solution are captured by insertion in thecrystal structure of the battery-type electrode.

The present disclosure also provides an electrochemical device forextracting lithium from an aqueous solution containing lithium ionscomprising at least one battery-type electrode comprising a porous orhigh surface substrate coated with a lithium insertion compound, whereinsaid device does not comprise a counter-electrode. In some aspects, thedevice further comprises a chloride reversible electrode or apolypyrrole reversible electrode. In some aspects, the substrate is acarbon substrate. In other aspects, the carbon substrate is a conductivesubstrate. In some aspects, the battery-type electrode comprises aconductive additive material. In some aspects, the conductive additivematerial is carbon black. In other aspects, the lithium insertioncompound comprises a manganese oxide. In some aspects, the manganeseoxide comprises γ-MnO₂ and/or λ- MnO₂. In some aspects, the manganeseoxide has a spinel crystal structure. In some aspects, the manganeseoxide comprises LiMn₂O₄. In other aspects, the lithium insertioncompound comprises lithium cobalt oxide, lithium iron phosphate, lithiummanganese oxide, or combinations thereof. In some aspects, the lithiumcobalt oxide comprises LiCoO₂. In other aspects, the lithium ironphosphate comprises LiFePO₄. In some aspects, the battery-type electrodeis prepared by electrolytical delithiation of a porous or high surfacesubstrate coated with lithium cobalt oxide (LiCoO₂), lithium ironphosphate (LiFePO₄), lithium manganese oxide (LiMn₂O₄), or combinationsthereof. In some aspects, the carbon substrate is selected from thegroup consisting of carbon felt, carbon cloth, carbon paper, graphitegranules, granite foam, high surface area graphite fiber, andcombinations thereof. In some aspects, the carbon substrate is a carbonfelt. In some aspects, the carbon substrate is a calcined coke carbonsubstrate. In some aspects, the chloride reversible electrode comprisesa porous or high surface carbon substrate and silver metal particles. Insome aspects, the silver metal particles are nanoparticles. In someaspects, the chloride reversible electrode comprises an electricallyconductive polymer. In some aspects, the electrically conductive polymeris a polypyrrole. In other aspects, the lithium ions in the aqueoussolution are captured by insertion in the crystal structure of thebattery-type electrode. In some aspects, the battery-type electrode andchloride reversible electrode are positioned in separate half-cells. Insome aspects, the half-cell comprising the battery-type electrode andthe half-cell comprising the chloride reversible electrode or thepolypyrrole reversible electrode are separated by a semi-permeableelectrolysis membrane. In some aspects, the electrolysis membrane is anionomer membrane. In some aspects, the ionomer membrane is a NAFION®membrane. In some aspects, the NAFION® membrane is NAFION® 324. In someaspects, the half-cell comprising the battery-type electrode and thehalf-cell comprising the chloride reversible electrode or thepolypyrrole reversible electrode are not separated by a semi-permeableelectrolysis membrane. In some aspects, the half-cell comprising thebattery-type electrode and the half-cell comprising the chloridereversible electrode or the polypyrrole reversible electrode areseparated by a porous material. In some aspects, the porous material isa gauze. In some aspects, the gauze is a polyester gauze. In someaspect, the porous material is porous fritted glass.

The instant disclosure also provides a lithium extraction plant forextracting lithium from an aqueous solution containing lithium ionscomprising at least one electrochemical device as disclosed herein. Insome aspects, the aqueous solution containing lithium ions is a brine.In other aspects, the brine is obtained from a high-altitude salt lake.In some aspects, the lithium extraction plant is controlled by a cleanenergy voltage source. In other aspects, the clean energy voltage sourceis a solar power source.

The present disclosure also provides a method to manufacture high puritylithium comprising using the methods, electrochemical devices, or thelithium extraction plants disclosed herein.

The present disclosure also provides an electrochemical process forextracting lithium from an aqueous solution containing lithium ionscomprising using (a) the packed bed electrochemical cells disclosedherein, (b) the packed bed electrochemical reactors disclosed herein,(c) the lithium extraction methods disclosed herein, (d) theelectrochemical devices disclosed herein, (e) the lithium extractionplants disclosed herein, or (e) any combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a graph showing an X-ray diffraction pattern of a LiMn₂O₄standard.

FIG. 2 is a graph showing an X-ray diffraction pattern of a sample oflithium and manganese oxide (LiMn₂O₄) prepared in the laboratory andused in the assays to extract lithium from brine using electrochemicalion exchange.

FIG. 3 is an electron microscopy image of LiMn₂O₄ nanocrystals used toextract lithium from brine using electrochemical ion exchange.

FIG. 4 is an electron microscopy image of a conductive carbon feltelectrode.

FIG. 5 shows an electrochemical cell for the extraction of lithium frombrines. The cathode is inserted in the “S” half-cell, which contains thebrine. The anode is inserted in the “HCl” half-cell which contains a 0.1M HCl solution. A NAFION® ionomer membrane is interposed between bothhalf cells.

FIG. 6 shows a cyclic voltammogram of carbon felt electrodes embeddedwith LiMn₂O₄ at 50 mVs⁻¹ in 50 mM LiClO₄ aqueous solution. The chemicalintercalation of lithium ions in manganese oxides proceeds according tothe equation: LiMn₂O₄(LiMn^(III)Mn^(IV)O₄)→2α−MnO₂+Li⁺+e⁻.

FIG. 7(A) is a schematic representation of the FM100 typeelectrochemical reactor for the electrochemical extraction of lithiumfrom brines and concentration of lithium chloride solutions.

FIG. 7(B) shows the components of a disassembled FM100 typeelectrochemical reactor.

FIG. 8 is a photograph of a electrochemical reactor for the extractionof lithium ions from brines with brine circulation through the half-cellcontaining the cathode and lithium extraction solution in the anodeconnected to a titanium pump (Cole Parmer 75211 flow pump).

FIG. 9 shows current transients of lithium ion insertion into a LiMn₂O₄carbon loaded electrode at 0.2 V vs. Ag/AgCl, and lithium release at 1.2V vs. Ag/AgCl in a lithium perchlorate 50 mM aqueous solution.

FIG. 10 is a schematic representation of the oxidized/reduced states ofpolypyrroles, which on oxidation uptakes anions in order to maintainneutrality of charges and conversely on reduction releases the anionsinto solution.

FIG. 11A, B, and C show different view of the experimental setup used inthe polypyrrole/carbon Electrode and a LiMn₂O₄/carbon electrode systempresented in Example 7.

FIG. 12 shows an SEM micrograph of carbon fibers in a carbon feltcovered by LiMn₂O₄ crystals corresponding to the experimental setuppresented in Example 7.

FIG. 13 shows an SEM micrograph depicting the polypyrrole deposit oncarbon felts corresponding to the experimental setup presented inExample 7.

FIG. 14 shows transients corresponding to four lithium chloride capturesteps in the LiMn₂O₄/carbon felt cathode corresponding to theexperimental setup presented in Example 7.

FIG. 15 shows current transients for a sequence of lithium recoverysteps during which lithium was released from a LiMn₂O₄ electrodeaccording to the experimental conditions presented in Example 7.

FIG. 16 shows the evolution of the electrical charge during the releaseof lithium ions from the LiMn₂O₄/carbon electrode into the electrolyteaccording to the experimental conditions presented in Example 7.

FIG. 17 shows an SEM micrograph of coke particles loaded with LiMn₂O₄crystals corresponding to the experimental setup presented in Example 8.

FIG. 18 shows a Press Filter reactor (type FM100)with axial flux ofelectrolyte and perpendicular current flow. The reactor consists of (i)titanium current collectors, (ii) carbon felt support and petroleumcalcined coke carbon support of LiMn₂O₄ at one electrode, (iii) carbonfelt support and polypyrrole at the other electrode, (iv) a Teflonframework, and (v) a polyester gauze in undivided cells.

FIG. 19 shows charge and discharge transients corresponding to thecapture and release of lithium ions by a LiMn₂O₄ electrode according toexperimental conditions presented in Example 8.

FIG. 20 shows discharge and charge curves at constant current (±0.5mA/cm²) during 2 hours by a LiMn₂O₄ electrode according to experimentalconditions presented in Example 8.

FIG. 21 shows a potential-charge curve for a LiMn₂O₄ electrode accordingto experimental conditions presented in Example 8.

FIG. 22 shows a three dimensional reactor at the laboratory scale withcoke compact bed electrodes loaded respectively with LiMn₂O₄ andpolypyrrole corresponding to the experimental packed bed setup presentedin Example 8.

FIG. 23 shows a longitudinally packed bed cylindrical reactor prototypethat includes a glass cylinder with two compartments separated by porousfritted glass, titanium mesh current collectors with titanium rodelectrical connectors, two packed beds containing 20 g of coke loadedwith electrode materials, rubber stoppers, and tubing to connect to apiston flow pump.

FIG. 24 shows the pressure drop in the reactor shown in FIG. 23 measuredat different flow rates (0-30 mL per second) using a mercury pressuremeter.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses an efficient and environmentally benignmethod for the extraction of lithium value from aqueous electrolyticsolutions containing lithium ions together with other metal ions such assodium, potassium, magnesium, and chloride ions (e.g., chloride richbrines, sea water, etc.).

The method and the devices described herein selectively extract lithiumfrom solutions containing other ions, even when these other ions arepresent in relatively high concentrations. The present disclosure alsoprovides a clean technology for the rapid extraction of lithium with lowenergy consumption. In this respect, the methods and devices disclosedherein can be used to extract lithium from brines or salt deposits inhigh altitude lakes without altering the balance of water, unlike theevaporation methods used at present to recover lithium from salt lakesin South America and other locations. It should be noted that themethods disclosed herein can be applied, for example, to (i) artificialbrines containing only lithium or lithium and other salts, and (ii) tonatural brines. A person skilled in the art would appreciate thatmethods suitable for lithium extraction from artificial brinescontaining only lithium, lithium and low concentrations of other salts,or artificial brines with defined compositions, may be unable tosuccessfully extract lithium from natural brines containing not onlylithium but also high sodium concentrations and high concentrations ofmany other salts.

In particular, the present disclosure provides an electrochemicalprocess for the extraction of lithium from an aqueous solutioncontaining lithium ions comprising the insertion of lithium ions intothe crystal structure of a lithium insertion material, e.g., a manganeseoxide, embedded on a porous substrate, e.g., a carbon felt, in thecathode and the subsequent deinsertion (extraction) of lithium ions fromthe crystal structure of lithium saturated oxides in the anode. In someaspects, the lithium insertion material is supported by calcined cokecarbon particles.

Lithium recovery from sea water, which contains approximately 0.17 mg/Llithium, has been described in U.S. Patent Publ. No. 2011/0174739 usingan adsorption/desorption process with manganese oxide as adsorbent in apolymer membrane. Unlike the present invention, the adsorbed lithium inthe membrane is then released by treating with a hydrochloric acidsolution, resulting in the generation of large volume of chemical waste.The method disclosed herein avoids this drawback by using anelectrochemical approach in which a low valence metal cation is oxidizedin a battery-type lithium insertion electrode and chloride is releasedat the chloride reversible electrode by electro-reduction.

In one aspect, the electrochemical method disclosed herein comprises thereduction of Mn^(IV) ions of the cubic spinel manganese oxide MnO₂ toMn^(III), which then undergoes the spontaneous insertion of lithium ionspresent in the solution (e.g., a salt lake brine or sea water) into thecrystal structure of a LiMn₂O₄ oxide (or another suitable lithium ioninsertion material such as LiCoO₂, LiFePO₄, etc.). In the subsequentlithium concentration step of the method disclosed herein, Mn^(III) isoxidized to Mn^(IV) by reverting the electrochemical cell polarity, thusreleasing the inserted lithium ions present in the crystal structure ofthe ion insertion material to the aqueous solution. This results in anincrease in the lithium chloride concentration in the aqueous solution.

Likewise, the method can be generalized by using other lithium insertionmaterials, such as lithium compounds containing iron or cobalt. In thesecases, for example, oxidation of Co^(II) to Co^(III) or Fe^(II) toFe^(III), respectively in the LiFePO₄ and LiCoO₂ containing electrodesreleases lithium ions contained in their respective crystal structuresto the aqueous solution.

In both steps (lithium extraction and lithium release/concentration) thesecond electrode is a reversible electrode, for example, an Ag/AgClreversible electrode or a polypyrrole reversible electrode. For example,in the lithium extraction step an Ag/AgCl reversible electrode canuptake chloride ions from the solution to form insoluble silverchloride. Then, in the lithium release/concentration step, the Ag/AgClreversible electrode can release chloride to the solution by formationof metallic silver. Similarly, when a polypyrrole reversible electrodeis used in the lithium release/concentration step, the polypyrrolereleases chloride ions into the solution. Accordingly, the balance ofcharge in the electrochemical cell is maintained by chloride and lithiumions, and no hydrogen ion imbalance modifies the solution pH (this is acritical difference with respect to methods that use an inert counterelectrode, e.g., the process described in U.S. Pat. No. 5,198,081).

Definitions

The term, “lithium” as used herein refers to lithium metal, lithiumions, lithium atoms, or lithium compounds depending on the context. Theterm “lithium compounds” in reference to lithium products extracted froman aqueous solution containing lithium ions comprises, for example,lithium chloride, lithium hydroxide, lithium phosphate, lithiumcarbonate, etc.

The term “battery-type electrode” as used herein refers to an electrodecomprising components commonly found in lithium-battery cathodes, suchas lithium manganese oxides with a spinel structure. Normal spinelstructures are usually cubic closed-packed oxides with one octahedraland two tetrahedral sites per oxide. The tetrahedral points are smallerthan the octahedral points. Trivalent cations (B³⁺) occupy theoctahedral holes because of a charge factor, but can only occupy half ofthe octahedral holes. Divalent cations (A2⁺) occupy ⅛ of the tetrahedralholes. A normal spinel is LiMn₂O₄.

In addition, there are intermediate cases where the cation distributioncan be described as (A_(1-x)B_(x))[A_(x/2)B_(1-x/2)]₂O₄, whereparenthesis ( ) and brackets [ ] are used to denote tetrahedral andoctahedral sites, respectively, and A and B represent cations. Theso-called inversion degree x adopts values between 0 (normal) and 1(inverse), and it is x=⅔ for a fully random cation distribution.

The term “lithium insertion compound” as used herein refers to acompound that can host and release lithium reversibly. In the insertionprocess, lithium ions are intercalated in the crystal structure of thehosting compound. The term intercalation as used herein refers to aproperty of a material that allows ions to readily move in and out ofthe crystal structure of the material without the material changing itscrystal structure.

The term “conductive substrate” as used herein refers to a substratefunctioning as an electrode. Therefore, the electrically conductivesubstrate used herein encompass those made from electrically conductivematerial and those obtained by coating, deposition or lamination of anelectrically conductive layer of a “conductive additive material” on thesurface of a non-electrically conductive substrate.

The term “conductive additive material” refers to an electricallyconductive composition that can be applied to an otherwisenon-conductive substrate to confer conductive properties to it. Theelectrically conductive additive material can include electricallyconductive particulate or non-particulate materials. For example, theconductive additive material can include electrically conductivematerials such as carbon black or carbon nanofibers. Other suitableelectrically conductive particulate materials include, but are notlimited to, metallic particulates (e.g., electrically conductive metalssuch as aluminum, silver, nickel, etc. in the form of a granule, flake,sphere of varying size and size distributions), non-electricallyconductive grade carbon black, particles or fibers coated withelectrically conductive materials, carbon fibers, inherently conductivepolymers (i.e., a class of polymeric materials having conjugated chainconfigurations giving them the intrinsic ability to transfer electronslike a semiconductor, such as polyacetylene or polyaniline).

The conductive additive material can also include a liquid component inwhich the electrically conductive material is dispersed. The liquidcomponent used in the conductive additive material can be selected froma variety of liquid components. Suitable liquid components include, butare not limited to, polyester vehicles, polyol vehicles, epoxies,plasticizers, monomers (e.g., styrene, divinyl benzene, vinyl toluene,etc.).

The term “substrate” as used herein refers to structures used during themanufacture of electrodes upon which other layers are fabricated, e.g.,a carbon felt upon which a manganese oxide is deposited. In someaspects, the substrate comprises calcined coke carbon particles. In someaspects, the coke carbon particles are generated by petroleumcalcination.

The term “nanoparticle” as used herein refers to a particle with atleast two dimensions of 100 nanometers (nm) or less. The termnanoparticle includes, for example, nanospheres, nanorods, nanofibers,including nanowires, nanobelts, nanosheets, nanocards, and nanoprisms.

The term “carbon black” as used herein refers to any of various finelydivided forms of carbon made by the incomplete combustion or thermaldecomposition of a carbonaceous fuel.

The term “carbon felt” as used herein refers to a textile material thatpredominantly comprises randomly oriented and intertwined carbon fibers,which are typically fabricated by carbonization of organic felts (see,e.g., IUPAC Compendium of Chemical Terminology 2^(nd) Edition (1997)).Most typically, organic textile fibrous felts are subject to pyrolysisat a temperature of at least 1200° K., more typically 1400° K., and mosttypically 1600° K. in an inert atmosphere, resulting in a carbon contentof the residue 99 wt %, more typically 95 wt %, and most typically 99 wt%. Carbon felts have a surface of at least about 0.01-100 m²/g, and moretypically 0.1-5 m²/g, most typically 0.3-3 m²/g. When carbon felt isactivated, it will typically have a surface area of more than 100-500m²/g, more typically at least about 500-1200 m²/g, and most typically atleast about 1200-1500 m²/g or even more. Depending on the organictextile material and carbonization conditions, the carbon felt can begraphitic, amorphous, have partial diamond structure (added or formed bycarbonization), or a mixture thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a”, “an” and “the” include plural referentsunless the context clearly dictates otherwise. The terms “a” (or “an”),as well as the terms “one or more,” and “at least one” can be usedinterchangeably herein.

Furthermore, “and/or” where used herein is to be taken as specificdisclosure of each of the two specified features or components with orwithout the other. Thus, the term “and/or” as used in a phrase such as“A and/or B” herein is intended to include “A and B,” “A or B,” “A,”(alone) and “B” (alone). Likewise, the term “and/or” as used in a phrasesuch as “A, B, and/or C” is intended to encompass each of the followingembodiments: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; Aand B; B and C; A (alone); B (alone); and C (alone).

Units, prefixes, and symbols are denoted in their Système Internationalde Unites (SI) accepted form. Numeric ranges are inclusive of thenumbers defining the range. The headings provided herein are notlimitations of the various aspects or embodiments of the invention,which can be had by reference to the specification as a whole. It isunderstood that wherever embodiments are described herein with thelanguage “comprising,” otherwise analogous embodiments described interms of “consisting of” and/or “consisting essentially of” are alsoprovided.

Electrochemical Method for Lithium Extracting

The present disclosure provides an electrochemical method for extractinglithium from an aqueous solution containing lithium ions comprising:

-   -   i. contacting two electrodes with an aqueous solution containing        lithium ions wherein the electrodes (an anode and a cathode) are        a battery type electrode, and a chloride reversible electrode        (“lithium extraction step”);    -   ii. applying a voltage or circulating a current between the two        electrodes (being the cathode negative and the anode positive        during lithium extraction step), wherein the lithium ions are        captured by the battery-type electrode; and,    -   iii. exchanging the aqueous solution containing lithium ions        with a dilute solution of lithium chloride and reversing the        electrical polarity, thus releasing lithium ions into the dilute        solution (“lithium release/concentration step”).

In some aspects, steps (ii) and (iii) are repeated several times. Insome aspects, steps (ii) and (iii) are repeated 2 times. In someaspects, steps (ii) and (iii) are repeated 3 times. In some aspects,steps (ii) and (iii) are repeated 4 times. In some aspects, steps (ii)and (iii) are repeated more than four times.

In some aspects, the repetition of steps (ii) and (iii) can enrich theLi:Na concentration ratio in dilute solution with respect to the brineby at least 2-fold, at least 4-fold, at least 6-fold, at least 8-fold,at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold,at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold,at least 90-fold, at least 100-fold, at least 200-fold, at least300-fold, at least 400-fold, at least 500-fold, at least 600-fold, atleast 800-fold, at least 900-fold, at least 1000-fold, at least1100-fold, at least 1200-fold, at least 1300-fold, at least 1400-fold,at least 1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold,1900-fold, or at least 2000-fold.

In some aspects, the enrichment in the Li:Na concentration resultingfrom the repetition of steps (ii) and (iii) can be used to increase thepurify of the resulting lithium produced using the methods disclosedherein.

In some aspects, step (iii) is repeated several times. In some aspects,step (iii) is repeated 2 times. In some aspects, step (iii) is repeated3 times. In some aspects, step (iii) is repeated 4 times. In someaspects, step (iii) is repeated more than four times.

In some aspects, the repetition of steps (iii) can enrich the Li:Naconcentration ratio in dilute solution with respect to the brine by atleast 2-fold, at least 4-fold, at least 6-fold, at least 8-fold, atleast 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, atleast 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, atleast 90-fold, at least 100-fold, at least 200-fold, at least 300-fold,at least 400-fold, at least 500-fold, at least 600-fold, at least800-fold, at least 900-fold, at least 1000-fold, at least 1100-fold, atleast 1200-fold, at least 1300-fold, at least 1400-fold, at least1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold, 1900-fold,or at least 2000-fold. In some aspects, the repetition of step (iii) canenrich the Li:Na concentration in the brine more than 2000-fold.

In some aspects, the repetition of step (iii) can enrich the Li:Naconcentration in the brine more than 2000-fold. In some aspects, theenrichment in the Li:Na concentration resulting from the repetition ofstep (iii) can be used to increase the purify of the resulting lithiumproduced using the methods disclosed herein.

In some aspects, the aqueous solution obtained in step (iii) can be usedas the aqueous solution containing lithium ions of step (i), and steps(i) to (iii) can be performed recursively using the aqueous solutionfrom each successive step (iii) as the aqueous solution containinglithium ions of the next step (i). In some aspects, the step sequence(i)-(iii) is repeated 2 times, wherein the aqueous solution from eachsuccessive step (iii) is used as the aqueous solution containing lithiumions of the next step (i). In some aspects, the step sequence (i)-(iii)is repeated 3 times, wherein the aqueous solution from each successivestep (iii) is used as the aqueous solution containing lithium ions ofthe next step (i). In some aspects, the step sequence (i)-(iii) isrepeated 4 times, wherein the aqueous solution from each successive step(iii) is used as the aqueous solution containing lithium ions of thenext step (i). In some aspects, the step sequence (i)-(iii) is repeatedmore than 4 times, wherein the aqueous solution from each successivestep (iii) is used as the aqueous solution containing lithium ions ofthe next step (i).

In some aspects, the repetition of step sequence (i)-(iii), wherein theaqueous solution from each successive step (iii) is used as the aqueoussolution containing lithium ions of the next step (i), can enrich theLi:Na concentration ratio in dilute solution with respect to the brineby at least 2-fold, at least 4-fold, at least 6-fold, at least 8-fold,at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold,at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold,at least 90-fold, at least 100-fold, at least 200-fold, at least300-fold, at least 400-fold, at least 500-fold, at least 600-fold, atleast 800-fold, at least 900-fold, at least 1000-fold, at least1100-fold, at least 1200-fold, at least 1300-fold, at least 1400-fold,at least 1500-fold, at least 1600-fold, at least 1700-fold, 1800-fold,1900-fold, or at least 2000-fold. In some aspects, the repetition ofstep sequence (i) and (iii), wherein the aqueous solution from eachsuccessive step (iii) is used as the aqueous solution containing lithiumions of the next step (i), can enrich the Li:Na concentration in thebrine more than 2000-fold.

In some aspects, the repetition of step sequence (i)-(iii), wherein theaqueous solution from each successive step (iii) is used as the aqueoussolution containing lithium ions of the next step (i), can enrich theLi:Na concentration in the brine more than 2000-fold. In some aspects,the enrichment in the Li:Na concentration resulting from the repetitionof step sequence (i)-(iii), wherein the aqueous solution from eachsuccessive step (iii) is used as the aqueous solution containing lithiumions of the next step (i), can be used to increase the purify of theresulting lithium produced using the methods disclosed herein.

In some aspects, the disclosed process can be applied to diverse aqueoussolutions containing lithium, for example, sea water, lake water,underground water, hot-springs water, geothermal brines, oilfieldbrines, relict hydrothermal brines, etc. Thus, in some aspects, theaqueous solution can contain low concentrations of lithium (e.g., about0.17 ppm for sea water), whereas in other aspects the aqueouselectrolytic solution can contain high concentrations of lithium (e.g.,about 700 ppm brines from high altitude lakes).

In spine aspects, the lithium concentration in the aqueous electrolyticsolution is at least about 0.10 ppm, or at least about 0.12 ppm, or atleast about 0.14 ppm, or at least about 0.16 ppm, or at least about 0.18ppm, or at least about 0.20 ppm, or at least about 0.22 ppm, or at leastabout 0.24 ppm, or at least about 0.26 ppm, or at least about 0.28 ppm,or at least about 0.30 ppm. In some aspects, the lithium concentrationin the aqueous electrolytic solution is at least about 0.4 ppm, or atleast about 0.5 ppm, or at least about 0.6 ppm, or at least about 0.7ppm, or at least about 0.8 ppm, or at least about 0.9 ppm, or at leastabout 1 ppm. In other aspects, the lithium concentration in the aqueouselectrolytic solution is at least about 2 ppm, or at least about 3 ppm,or at least about 4 ppm, or at least about 5 ppm, or at least about 6ppm, or at least about 7 ppm, or at least about 8 ppm, or at least about9 ppm, or at least about 10 ppm. In other aspects, the lithiumconcentration in the aqueous electrolytic solution is at least about 20ppm, or at least about 30 ppm, or at least about 40 ppm, or at leastabout 50 ppm, or at least about 60 ppm, or at least about 70 ppm, or atleast about 80 ppm, or at least about 90 ppm, or at least about 100 ppm.In other aspects, the lithium concentration in the aqueous electrolyticsolution is at least about 150 ppm, or at least about 200 ppm, or atleast about 250 ppm, or at least about 300 ppm, or at least about 350ppm, or at least about 400 ppm, or at least about 450 ppm, or at leastabout 500 ppm, or at least about 550 ppm, or at least about 600 ppm, orat least about 650 ppm, or at least about 700 ppm, or at least about 750ppm, or at least about 800 ppm, or at least about 850 ppm, or at leastabout 900 ppm, or at least about 950 ppm, or at least about 1000 ppm.The method disclosed herein is applicable to any lithium containingaqueous electrolytic solution, e.g., a solution containing lithiumchloride, lithium carbonate, lithium hydroxide, lithium sulfate, lithiumnitrate, lithium phosphate, etc.

In some aspects, the disclosed methods can be applied to aqueoussolutions comprising lithium ions and contaminant non-lithium metal ions(e.g., sodium, potassium, etc.) and/or non-metal ions (e.g., chloride,sulfate, carbonate, nitrate, etc.). Conversely, the disclosed methodscan be applied to solutions containing a purified or partially purifiedsingle lithium compound such as lithium carbonate in order to producelithium chloride.

The disclosed methods can also be applied by maintaining the electricalpolarity, and reversing the half-cells in which each electrode islocated, instead of maintaining the location of the electrodes andreversing the electrical polarity.

In some aspects, the dilute lithium chloride solution in the “lithiumrelease/concentration step” can be replaced with a dilute lithiumperchlorate solution. Lithium perchlorate is generally used as an inertelectrolyte in lithium batteries.

Lithium containing ore (e.g., spodumene, petalite, amblygonite, lithiamicas such as zinnwaldite or lepidolite) can also be used as a sourceprovided that a lithium-containing aqueous electrolytic solution isproduced therefrom. In some aspects, an aqueous electrolytic solutionsuitable to use in the methods disclosed herein can be prepared bydissolving natural deposits (e.g., salt deposits from high altitude saltlakes or subsurface evaporitic salt deposits) or artificial deposits(e.g., salt deposits from salt works).

In some aspects, prior to purification according to the electrochemicalmethods disclosed herein, impurities (e.g., ions other than lithium,such as metal or non-metal ions) present in the aqueous electrolyticsolution can be reduced or removed via suitable processes known in theart for removing or reducing the respective impurities (e.g.,precipitation or ion exchange).

In some aspects, the voltage or circulating current can be provided by aconventional (e.g., electricity generated from conventional fossil-fuelsources such as coal or gas, or nuclear power) or a clean energy source,for example solar energy (e.g., from thermal or photovoltaicgenerators). Other clean energy sources can be used, for example, energyobtained from hydroelectric generators, biomass, geothermal sources,wind energy, wave/tidal energy, landfill gas, or gas powered fuel cells.

In some aspects, a small DC voltage is applied between the twoelectrodes, being the battery-type electrode negative and the chloridereversible electrode positive during the lithium extraction step. Insome aspects, the DC voltage is between about 0.1 and about 0.5 V. Insome aspects, the DC voltage is lower than 0.1 V. In other aspects, theDC voltage is higher than 0.5 V. In some aspects, the DC voltage is atleast about 0.1 V, or at least about 0.2 V, or at least about 0.3 V, orat least about 0.4 V, or at least about 0.5 V. Alternatively a DCcurrent can circulated with the same electrode polarity. In someaspects, the DC current is between 0.5 and about 1.0 mA.cm⁻². In someaspects, the DC current is lower than 0.5 mA.cm⁻². In other aspects, theDC current is higher than 1.0 mA.cm⁻². In some aspects, the DC currentis at least about 0.5 mA.cm⁻², or at least about 0.6 mA.cm⁻², or atleast about 0.7 mA.cm⁻², or at least about 0.8 mA.cm⁻², or at leastabout 0.9 mA.cm⁻², or at least about 1.0 mA.cm⁻².

In some aspects,, the extractive electrochemical processes disclosedherein can be operated under constant potential. In other aspects, theextractive electrochemical processes disclosed herein can be operatedunder current control.

In some aspects, after contacting the aqueous solution with theelectrodes and applying the DC voltage between the electrodes, theaqueous electrolytic solution can be exchanged by a dilute aqueoussolution (e.g., a dilute lithium chloride solution) in order to provideohmic conductivity to the electrochemical cell, and the electricalpolarity can then be reversed. In this step, the battery-type lithiuminsertion electrode (e.g., carbon felt loaded with manganese dioxide) isthe positive electrode, and manganese ions (or cobalt, iron, etc.depending on the lithium insertion compound used) can be oxidized torelease lithium ions into the dilute solution. As a result, theconcentration of lithium ions increases in the dilute aqueous solution.Conversely, the chloride reversible electrode (e.g., a silver/silverchloride electrode or a polypyrrole electrode) is the negativeelectrode. When the material in the negative electrode is reduced, forexample, the polypyrrole or the silver chloride are reduced (e.g., tosilver) releasing chloride ions to form a lithium chloride concentratedsolution.

In some aspects, the concentration of lithium chloride in the dilutesolution prior to reversing the electrolytic polarity is about 50millimolar. In some aspects, the concentration of lithium chloride inthe dilute solution prior to reversing the electrolytic polarity is atleast about 10 millimolar, or at least about 15 millimolar, or at leastabout 20 millimolar, or at least about 25 millimolar, or at least about30 millimolar, or at least about 35 millimolar, or at least about 40millimolar, or at least about 45 millimolar, or at least about 50millimolar, or at least about 55 millimolar, or at least about 60millimolar, or at least about 65 millimolar, or at least about 70millimolar, or at least about 75 millimolar, or at least about 80millimolar, or at least about 85 millimolar, or at least about 90millimolar, or at least about 95 millimolar, or at least about 100millimolar.

The battery-type lithium insertion electrode disclosed herein cancomprise a porous or high surface substrate and a lithium insertioncompound. The porous or high surface substrate can be, for example, aconductive porous carbon felt, reticulated vitreous carbon, calcinedcoke carbon, or any other large area conductive carbon electrodematerial in which a lithium insertion material can be embedded.

Any high surface or porous carbon structure, or combinations thereof,can be used to make the electrodes disclosed herein. For example, theelectrodes can be made using carbon cloth, carbon paper, graphitegranules, graphite foam, high surface area graphite fiber, calcined cokecarbon, etc. Non-carbon based conductive porous substrates can also beused. In some aspects, the substrate is a high surface compositematerial comprising a carbon component, e.g., carbon powder or carbonfibers and/or calcined coke carbon, and a non-carbon binder. In someaspects, the electrodes can be made using combinations of carbonmaterials (e.g., a carbon cloth sleeve containing a carbon-based foam orcarbon granules, or calcined coke carbon).

In some aspects, the lithium insertion electrode comprises a highsurface or porous substrate comprising calcined coke carbon particles.In some aspects, the calcined coke carbon particles are obtained bypetroleum calcination. In some aspects, the calcined coke carbonparticles have a diameter of about 200 to about 800 micrometers. In someaspects, the calcined coke carbon particles have a diameter of at leastabout 100, at least about 200, at least about 300, at least about 400,at least about 500, at least about 600, at least about 700, at leastabout 800, at least about 900, or at least about 1000 micrometers. Insome specific aspects, the calcined coke carbon particles have adiameter of about 500 micrometers.

In some aspects, the carbon felt substrate has a surface area of about500 to about 3000 m²g⁻¹. To some aspects, the carbon felt substrate hasa surface area of at least about 500, at least about 600, at least about700, at least about 800, at least about 900, at least about 1000, atleast about 1100, at least about 1200, at least about 1300, at leastabout 1400, at least about 1500, at least about 1600, at least about1700, at least about 1800, at least about 1900, at least about 2000, atleast about 2100, at least about 2200, at least about 2300, at leastabout 2400, at least about 2500, at least about 2600, at least about2700, at least about 2800, at least about 2900, or at least about 3000m²g⁻¹.

These porous substrates can be used to prepare the battery-type lithiuminsertion electrode, the chloride reversible electrode, or both.

In some aspects, the carbon substrate is a conductive carbon substrate(e.g., a carbon nanotube substrate or a graphite-based substrate).However, in cases where the substrate is non-conductive the battery-typelithium insertion electrode can include a conductive additive material.In some aspects, the conductive additive material is carbon black, forexample, SHAWINIGAN BLACK® or VULCAN® carbon black. Accordingly, thebattery-type lithium insertion electrodes can be prepared by applying aslurry composed of a lithium insertion compound (e.g., a lithiummanganese oxide) and a conductive additive material (for example, carbonblack) suspended in a suitable solvent to a porous conductive substrate,for example, a carbon felt and/or calcined coke carbon particles (e.g.,petroleum calcined coke carbon particles).

The lithium insertion compound is typically a lithium insertion oxidesuch as a lithium manganese oxide. The lithium manganese oxide is aprecursor for producing a manganese oxide that can be used as anion-sieve type lithium adsorbent. Thus, in some aspects, thebattery-type lithium insertion electrode can comprise a carbon feltand/or petroleum calcined coke carbon (e.g., petroleum calcined cokecarbon particles) embedded with an lithium insertion materialcomprising, but not limited to, γ-MnO₂ and/or λ-MnO₂. In some aspects,the lithium insertion manganese oxide is γ-MnO₂. In some aspects, thelithium insertion manganese oxide is λ-MnO₂.

Once the battery-type lithium insertion compound has been incorporatedinto the battery-type lithium insertion electrode, the battery-typelithium insertion compound can be electrochemically delithiated. Theelectrochemical removal of lithium ions from the crystal structure ofthe battery-type lithium insertion compound leaves voids in the crystalstructure, therefore producing an ion-sieve type manganese oxide thancan be used as a high selectivity lithium adsorbent. Accordingly, whenthe ion-sieve type manganese oxide is exposed to the aqueous solutioncontaining lithium ions during the lithium extraction step, the voids inthe crystal structure of the manganese oxide can be filled with lithiumfrom the aqueous solution containing lithium ions.

In some aspects, the lithium insertion oxide comprises an oxide ofmanganese having a structure of spinel, particularly a spinel structurewith a 3D tunnel structure. As an example, the manganese oxide can beLi_(n)Mn_(2-x)O₄, where 1≦n≦1.33, 0≦x≦0.33, and n≦1+x, for exampleLi_(1.33)Mn_(1.67)O₄ or Li_(1.6)Mn_(1.6)O₄.

In some aspects, the manganese oxide is LiMn₂O₄ however, otherbattery-type lithium insertion compounds can be used, such as lithiumcobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), etc. Otherlithium insertion materials known in the art include, e.g., lithiumnickel manganese oxides (see, e.g., Ohzuku et al., Journal of MaterialsChemistry 21:10179-10188 (2011)); lithium nickel oxides (see, e.g.,Ohzuku et al., Journal of Materials Chemistry 21:10179-10188 (2011));cobalt vanadium oxides (see, e.g., Hibino et al., Electrochem.Solid-State Lett 8:A500-A503 (2005)); molybdenum oxides (see, e.g., Leeet al., Advanced Materials 20:3627-3632 (2008); vanadium oxides (see,e.g., Liu et al., Advanced Materials 14:27-30 (2002)); inverse spinelvanadates like LiNiVO₄ (see, e.g., Broussely et al., Electrochimica Acta43:3-22 (1999)); or lithium manganese oxides further comprisingtrivalent metals such as aluminum, chromium, gallium, indium or scandium(see, e.g., PCT Publ. No. WO 01/24293). In some aspects, thebattery-type lithium insertion electrode comprises a single battery-typelithium insertion compound. In other aspects, the battery-type lithiuminsertion electrode can comprise more than one battery-type lithiuminsertion compound.

The reversible chloride electrode can also comprise a porous or highsurface carbon substrate (e.g., a carbon felt or calcined coke carbon,as disclosed above) and metal particles, for example, silver metalparticles. In some aspects, the silver particles can be nanoparticles.Methods to deposit metal particles or a metal coating on a substrate arewell known in the art, for example, using layer-by-layer deposition.Thus, in some aspects, the reversible chloride electrode can comprisesilver nanoparticles supported in a conductive carbon felt on which theyhave deposited by layer-by-layer deposition of silver ions. These silverions are entrapped in a polyelectrolyte multilayer on the carbon feltfibers, which by chemical or electrochemical reduction can yield silvernanoparticles of large surface area. In turn, these silver nanoparticlescan react with chloride ions to form silver chloride.

In some aspects, the reversible chloride electrode comprises a highsurface or porous substrate comprising calcined coke carbon particles.In some aspects, the calcined coke carbon particles can be obtained bypetroleum calcination. In some aspects, the calcined coke carbonparticles have a diameter of about 200 to about 800 micrometers. In someaspects, the calcined coke carbon particles have a diameter of at leastabout 100, at least about 200, at least about 300, at least about 400,at least about 500, at least about 600, at least about 700, at leastabout 800, at least about 900, or at least about 1000 micrometers. Insome specific aspects, the calcined coke carbon particles have adiameter of about 500 micrometers.

Non-silver metal containing electrodes can be employed to makereversible chloride electrodes. For example, alternative chloridereversible electrodes comprising electrically conductive polymers (e.g.,polypyrrole/chloride, polyanilines, polyphenols, etc.) can be used.Thus, in some aspects, the chloride reversible electrode can comprise aconductive polymer such as polypyrrole which can uptake and releasechloride ions.

Other conducting polymers having good electrochemical activity, such aspolyaniline, polythiophene, polyimide, polyacetylene, polyphenylenevinylene, polyphenylene sulfate, or combinations of conducting polymerscan be used to make reversible chloride electrodes. See, for example,Imisides et al., Electroanalysis 3: 879-889 (2005); Bidan, Sensor andActuators b: Chemical 6:45-56 (1992); Walram & Bargon, Canadian Journalof Chemistry 64:76-95 (1986); Mermilliod et al. Journal of theElectrochemical Society 133:1073-1079 (1986); Roth & Graupner, SyntheticMetals 57:3623-3631 (1993), all of which are herein incorporated byreference in their entireties.

In some aspects, the polypyrrole reversible chloride electrode can alsocomprise a porous or high surface carbon substrate (e.g., a carbon feltand/or calcined coke carbon particles, as disclosed above). Methods toproduce a polypyrrole coating on a substrate are well known in the art,for example, using chemical polymerization on the substrate. Thus, insome aspects, the reversible chloride electrode can comprise polypyrroleformed by chemical polymerization onto a conductive carbon felt and/orcalcined coke carbon particles. Then, the polypyrrole can react withchloride. In some aspects, the polypyrrole reversible chloride electrodecan include other components such a dopants. In some aspects, thepolypyrrole reversible chloride electrode can contain silver, forexample silver particles (e.g., nanoparticles) entrapped in polymerizedpolypyrrole films or coatings. See, e.g., Song & Shiu. Journal ofElectroanalytical Chemistry 498:161-170 (2001).

Electrochemical Device for Lithium Extraction

The present disclosure also provides an electrochemical device forextracting lithium from an aqueous solution containing lithium ionscomprising at least one battery-type lithium insertion electrodecomprising a porous or high surface substrate coated with a lithiuminsertion compound, wherein the device does not comprise acounter-electrode. In some aspects, the electrochemical device furthercomprises a chloride reversible Electrode, e.g., an Ag/AgCl orpolypyrrole chloride reversible electrode. Battery-type lithiuminsertion electrodes and chloride reversible electrodes suitable for usein the electrochemical device of the present disclosure have beendescribed in detail above.

The electrochemical device disclosed herein can comprise twocompartments or half-cells, each composed of an electrode immersed in asolution of electrolyte. These half-cells are designed to contain theoxidation half-reaction and reduction half-reaction separately. In someaspects, the battery-type lithium insertion electrode and the chloridereversible electrode are positioned in separate half-cells. In someaspects, the half-cell comprising the battery-type lithium insertionelectrode and the half-cell comprising the chloride reversible electrodeare separated by a semi-permeable electrolysis membrane, such as anionomer membrane (e.g., a NAFION® membrane). In some aspects, theNAFION® membrane is NAFION® 324. Any available semi-permeableelectrolysis membrane which selectively passes cations and inhibits thepassage of anions can be employed in the present device. Such membranesare well known to those skilled in the art. In some aspects, no membraneis used. In some aspects, as porous material separates the half cells.In some aspects, the porous material can be a gauze. In some aspects,the gauze can be a polyester gauze. In some aspects, the porous materialcan be porous fritted glass.

In some aspects, the electrochemical device is a packed bed reactor. Inthis reactor configuration, the battery-type lithium insertion electrodematerials and the chloride reversible electrode materials (e.g., porousparticles such as calcined coke carbon particles loaded, for example,with either LiMn₂O₄ or polypyrrol) are placed between a currentcollector (e.g., a titanium collectors) and a separating porous barrier(e.g., a polyester gauze). In some aspects, the packed bed reactor doesnot comprise a semi-permeable electrolysis membrane separating thecathodic and anodic compartments.

In some aspects, the lithium extracting particles in the packed bedreactor comprise about 13 g of LiMn₂O₄ per 60 g of calcined cokeparticles. In some aspects, the lithium extracting particles contain atleast about 1 g, at least about 2 g, at least about 3 g, at least about4 g, at least about 5 g, at least about 6 g, at least about 7 g, atleast about 8 g, at least about 9 g, at least about 10 g, at least about11 g, at least about 12 g, at least about 13 g, at least about 14, or atleast about 15 g of LiMn₂O₄ per 60 g of calcined coke particles.

In some aspects, the aqueous solution is directly fed to anelectrochemical device for lithium extraction. In other aspects, theaqueous electrolytic solution can be concentrated with respect tolithium content. In yet other aspects, impurities are removed from theaqueous electrolytic solution, which is subsequently concentrated withrespect to the lithium content.

In some aspects, the electrochemical device can be constructed, forexample, using a FM100 press filter electrochemical reactor format asdisclosed in Example 4. In one aspect, the electrochemical devicecomprises two current collector contacts (e.g., stainless steel metalplates) which are in contact with the carbon felt electrodes (e.g.,battery-type lithium insertion electrode and chloride reversibleelectrode, respectively). The battery-type lithium insertion electrodeand reversible electrodes are mounted on insulating supports (e.g.,TEFLON® frames), and flow field channels allow the solutions tocirculate. Insulators allowing solutions to circulate (e.g., TEFLON® netseparators) are intercalated between each electrode to prevent shortcircuit of the electrodes. The reactor is held together by insulatedscrews that go through all the component plates. The system isexpandable to several electrodes in a stack (see FIG. 7A and 7B).

In some aspects, the FM100 electrochemical reactor can be assembledaccording to the FM100 electrochemical cell format disclosed in Example8. Accordingly, in some aspects, the reactor comprises current collectorcontacts (e.g., titanium metal plates) that are in contact with carbonfelt electrodes comprising a functionalized porous substrate. Forexample, one electrode comprises a carbon felt comprising calcinedpetroleum coke carbon particles supporting a battery-type lithiuminsertion electrode material (e.g., LiMn₂O₄), whereas the otherelectrode comprises a carbon felt comprising calcined petroleum cokecarbon particles supporting a chloride reversible electrode material(e.g., polypyrrole). The electrodes are separated by a non-membranousporous material (for example, a polyester gauze or porous fritted glass)which can optionally be mounted on a suitable support (e.g., a TEFLON®frame). In order to increase the production of lithium, severalundivided electrochemical cells can be stacked and connected in series.The same current can circulated through all the electrochemical cells inseries. See FIG. 18.

In some aspects, the electrochemical reactor is a packed bed reactorassembled according to the packed bed electrochemical cell formatdisclosed in Example 8. Accordingly, in some aspects the electrodescomprise a functionalized porous substrate (e.g., calcined petroleumcoke carbon) without a carbon felt substrate. In this configuration, oneelectrode comprises a compartment packed with calcined petroleum cokecarbon particles supporting a battery-type lithium insertion electrodematerial (e.g., LiMn₂O₄), whereas the other electrode comprises acompartment packed with calcined petroleum coke carbon particlessupporting a chloride reversible electrode material (e.g., polypyrrole).Both compartments can be separated by a non-membranous porous material,for example porous fritted glass. The reactor also comprises currentcollection contacts which are in contact with the electrodes. In someaspects, titanium mesh current collectors with titanium rod electricalconnectors can be used. See FIG. 22 and FIG. 23.

In some cases, the packed bed reactor can comprise 2, 3, 4, 5, 6, 7, 8,9, 10, or more than 10 of the packed bed electrochemical cells disclosedabove. A person skilled in the art would appreciate that theelectrochemical cells disclosed herein can be assembled in variousconfigurations, e.g., in series or in parallel, and also that the cellsdisclosed herein could be combined in series or in parallel with otherelectrochemical cells designed to extract other commercially valuableions from brines.

The term “non-membranous porous material” refers to materials such aswoven and nonwoven fabrics (e.g., gauzes), glass fiber mats, melt blownmats, felts, fritted glass, and the like. These porous non-membranousmaterials are used extensively as filtration media or as prefilters forfiltrations. Accordingly, the term non-membranous porous materialencompasses any materials known in the art that are suitable forfiltration or prefiltration, and in general to prevent the migration ofmacroscopic particles (e.g., carbon particles such as carbon blackparticles) between two or more separated compartments.

One skilled in the art would appreciate that other cell configurationsand materials can be used to (i) construct an electrochemical devicecomprising the battery-type lithium insertion electrode and the chloridereversible electrode disclosed in the instant application and (ii) tooperate such electrochemical device according to the methods disclosedherein. For example, instead of stainless steel or titanium plates ormeshes the electrochemical device can use any other corrosion-resistantmetal, alloy, or conductive synthetic material or composite. Inaddition, insulators (if used) can be built using TEFLON®, KAPTON®,MYLAR®, polyurethane, PVC, silicone rubber, glass, etc. See, forexample, M. I. Ismail, Ed, “Electrochemical reactors their science andtechnology—Part A: Fundamentals, electrolysers, batteries and fuelcells”. Elsevier, Amsterdam, The Netherlands, 1989. ISBN 0-444-87139-X;

Stainless steel, plastic tubing or other suitable tubing allows thebrine and clean electrolyte, respectively, to circulate through thethree-dimension expanded carbon felt electrodes containing the activematerials (e.g., manganese oxide, silver deposit, silver nanoparticles,polypyrrole).

The electrochemical device can connected through the current collectorcontacts to an external power supply which uses power obtained, e.g.,from a clean energy source such as solar energy, wind energy, geothermalenergy, etc. The aqueous solution containing lithium ions (e.g., a brinefrom a high altitude salt lake) and the dilute solution of lithiumchloride can be circulated through the device at a constant flow. Insome aspects, the solutions can be circulated at a variable flow. Insome aspects, solutions are circulated at about 20 to about 50mL/minute. In some cases, solutions are circulated at flow rates lowerthat about 20 mL/minute. In other cases, solutions are circulated atflow rates higher than about 50 mL/minute. In some cases solutions arecirculated at flow rates of about 5 mL/minute, or about 10 mL/minute, orabout 15 mL/minute, or about 20 mL/minute, or about 25 mL/minute, orabout 30 mL/minute, or about 35 mL/minute, or about 40 mL/minute, orabout 45 mL/minutes, or about 50 mL/minute, or about 55 mL/minute, orabout 60 mL/minute, or about 65 mL/minute, or about 70 mL/minute, orabout 75 mL/minute.

In some aspects, more than one electrochemical device can be operatedsimultaneously via the some voltage or current source. In this case, theelectrochemical devices can be operated either in series or in parallel.In other aspects, each electrochemical device is operated with aseparate voltage or current source.

Electrochemically Purified Lithium

In some aspects, the methods and devices disclosed herein can be used toproduce a very high purity lithium chloride solution that can becrystallized and used to produce lithium metal with extremely low levelsof impurities (e.g., for battery components). Accordingly, in someaspects, the disclosed method and devices can produce lithium chlorideat a purity level of least about 99.9%. In other aspects, the lithiumchloride produced according to the disclosed methods and devices has apurity of at least about 99.99%. In other aspects, the lithium chlorideproduced according to the disclosed methods and devices has a purity ofat least about 99.999%. The high purity lithium can be electrolyzed intolithium metal.

Electrochemical Plant for Lithium Extraction

The present disclosure also provides an electrochemical plant to extractlithium and other valuable metals by using as feeding material brinesextracted from high altitude salt lakes. The electrochemical plantcomprises a plurality of electrochemical devices according to thepresent invention in which brines extracted from a high altitude saltlake are processed, and lithium is extracted according to the methodsdisclosed herein. The electrochemical plant can be operated using lowenvironmental impact energy sources such as solar energy, wind energy,or geothermal energy. The use of this type of energy source obviates theneed to construct high footprint power generation equipment or powertransmission lines. Furthermore, the use of clean energy sources reducesthe probability of environmental damage caused by fossil fuel spills orfume emissions in the high altitude ecosystem. The brines used asfeedstock for the plant can be obtained by drilling under the lakesurface, and the processed lithium-depleted brines can be reinjectedunder the lake surface, further reducing the environmental and visualimpact of the plant. This production process is highly advantageous overexisting technologies in that (i) the lithium-containing salt depositsdo not need to be dissolved in water, thus reducing loss of water fromthe high altitude ecosystem through evaporation, (ii) the process doesnot require added chemicals such as soda ash, and (iii) the process doesnot release by-products (e.g., sodium chloride) that can accumulate inthe high altitude salt lake.

A similar approach can be used to implement an electrochemical plant toextract lithium from sea water, in which the electrochemical plant canbe operated using low environmental impact energy sources such as solarenergy, wind energy, tidal energy, or geothermal energy and theprocessed lithium-depleted sea water is returned to the ocean.

In some aspects, the methods and devices disclosed herein can be used torecycle lithium. According to this approach, metallic lithium extractedfrom, e.g., lithium batteries, is dissolved to yield a lithium salt thatcan be processed by using the methods and devices disclosed herein toproduce highly pure lithium. In other aspects, the methods and devicesdisclosed herein can be used to refine lithium. According to thisapproach, lithium obtained at low purity levels using the methods anddevices disclosed herein or obtained using traditional methods can befurther refined using the methods and devices disclosed herein in orderto generate high purity lithium.

Equivalents

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

All publications, patents, and patent applications referred to hereinare expressly incorporated by reference in their entireties.

EXAMPLES Example 1 LiMnO₄ Preparation

LiMn₂O₄ was synthesized using solid state chemistry, 0.377 g of Li₂CO₃(Aldrich) and 1.74 g of MnO₂ (Aldrich) were thoroughly mixed at a molar0.51:2 ratio in a mortar, and heated at 350° C. for 12 hours. Sampleswere subsequently heated at 800° C. for 24 hours with 3 cycles ofgrinding and firing. The resulting powder was characterized by scanningelectron microscopy (SEM) and X-ray Diffraction (XRD).

An X-ray diffractogram of a LiMn₂O₄ sample obtained according to themethod described above is shown in FIG. 2. The comparison of suchdiffractogram with an X-ray diffractogram of a LiMn₂O₄ standard (FIG. 1)indicated that a single phase mixed oxide was obtained. SEM examinationof the resulting LiMn₂O₄ samples showed very well formed crystals withaverage size of several nanometers to a micrometer (see FIG. 3).

Example 2 Preparation of Carbon Felt Embedded with LiMn₂O₄

Conductive carbon felt electrodes (National Electric Carbon Products, adivision of Morgan Specialty Graphite; Greenville, S.C., US) were cutinto 20×10×3 mm pieces, thoroughly washed with 1:1 isopropanol:Milli-Qwater and finally rinsed with Milli-Q water (FIG. 4).

The synthesized LiMn₂O₄ powder was loaded onto the carbon felt electrodeas a slurry prepared with 80% Li—Mn oxide, 10% carbon black (ChevronPhillips SHAWINIGAN BLACK®) and 10% PVC (polyvinyl chloride) indichloromethane. Subsequently, the carbon felts were dried at 60° C.under vacuum during 24 hours.

The LiMn₂O₄ loaded carbon felt electrodes were subsequently subjected toelectrolysis to de-lithiate the oxide while keeping the highly selectivecrystal structure to allow the intercalation of lithium ions. The oxideloaded carbon electrode was placed in one of the compartments in a twocompartment TEFLON® cell, and a platinum counterelectrode was placed inthe second compartment. Both compartments were separated by a NAFION®324 membrane (E.I. du Pont de Nemours and Company). A silver/silverchloride 3 M KCl reference electrode was used and 0.1 M sodium chlorideor 0.1 M hydrochloric acid was used as electrolyte.

The intercalation-deintercalation of lithium ions was characterized bycyclic voltammetry in a 6 mL two-compartment TEFLON® cell separated by aNAFION® 324 membrane. Cyclic voltammetry measurements were conductedusing an Autolab PG30 potentiostat (Eco Chemie, Netherlands) (see FIG.5).

The resulting voltammograms are shown in FIG. 6. The cyclic voltammetrydata (50 mVs⁻¹) was consistent with the insertion lithium in the crystalstructure of the manganese dioxide during the reduction cycle and therelease of lithium ions from the crystal structure of the manganesedioxide during the oxidation cycle as described by Cairns et al.(Journal of The Electrochemical Society 146:4339-4347 (1999)). Theobserved reaction was LiMn₂O₄ (LiMn^(III)Mn^(IV)O₄)→2α−MnO₂+Li⁺+e⁻,which corresponds to the oxidation of Mn(III) ions in the mixed oxidelattice and expulsion of lithium ions into solution during the anodiccycle.

Example 3 Preparation of Silver Chloride Reversible Electrodes

Several approaches were used to prepare chloride reversible electrodes.

In one chloride reversible electrode preparation, silver was directlydeposited from a commercial silver cyanide bath (Argex, Laring S.A.,Argentina) by holding the potential of the carbon felt at −0.1 V. Thesilver cyanide bath had been previously sonicated in isopropanol for 30minutes and rinsed with Milli-Q water. Silver crystals of 100 nanometersto 1 micrometer were obtained on the conductive carbon fibers.

In another chloride reversible electrode preparation, a layer-by-layerpolyelectrolyte multilayer was deposited on the carbon fibers asdescribed, for example, in Rubner et al., Langmuir 18:3370-75 (2002),and Vago et al., Chem. Commun. 5746-48 (2008). The polyelectrolytemultilayer functioned as a nanoreactor to confine the silver ions. Thesilver ions were further reduced chemically with 5 mM sodium borohydrideor reduced electro-chemically to yield large surface area nanoparticleson the carbon fibers.

In another preparation, ten millimolar poly(acrylyc acid) and poly(allylamine) were self-assembled layer by layer by sequential dippingthe carbon felt in the respective polyelectrolyte solution with rinsingbetween dipping steps. Then, the modified carbon felt was subject tosilver ion exchange by dipping it in a 10 to 50 millimolar silvernitrate solution in water, rinsing in distilled water, and reducingchemically or electrochemically. The resulting nanoparticles depositedonto the carbon fibers of the felt were examined by SEM and furthercharacterized by cyclic voltammetry in 50 millimolar lithium chloride.

Example 4 Construction of Electrochemical Reactor

A FM100 press filter electrochemical reactor for the extraction oflithium from chloride containing brines, salt water, hot-spring water,etc., was built in stainless steel with a plastic separator between thetwo carbon felts electrodes (reversible to lithium, and reversible tochloride ions, respectively), as depicted in FIG. 7.

The electrochemical cell shown schematically in FIG. 7A was constructedusing 5 mm stainless steel plates (B), and thin TEFLON® plates (G). Two2 mm stainless steel plates (FP) acted as current collectors and were incontact with the carbon felt electrodes in TEFLON® frames (S), with flowfield channels to circulate the liquid. A TEFLON® net separator wasintercalated between each carbon felt electrode (46×156×3 mm, approx. 60cm² cross section), i.e., lithium insertion electrode, and chloridereversible electrode, to prevent short circuit of the conducting carbonelectrodes. The sandwich cell was held together by insulated screws thatwent through all the component plates. The system is expandable toseveral electrodes in a stack.

Stainless steel or plastic tubing allowed the brine and cleanelectrolyte, respectively, to circulate through the three-dimensionexpanded carbon felt electrodes containing the active materials(manganese oxide and silver deposit or nanoparticles respectively).

The electrochemical cell was connected through the current collectorcontacts to an external power supply. The brine and clean recoveryelectrolyte were circulated at variable flow, typically 20 to 50 mL/minwith a Cole-Parmer 75211 flow pump (Cole-Parmer, Vernon Hills, Ill.).The cell potential was controlled with a potentiostat/galvanostat(Radiometer DEA 332 (Radiometer, Denmark) or Autolab PG30 (EcoChemie,Netherlands) with a 20 Ampere current booster). The selectivity forLi⁺/Na⁺ depended on the relative concentrations of the cations, withlarger selectivity for lithium concentrated solutions (large Li⁺/Na⁺)(FIG. 8).

Example 5 Lithium Extraction-Release Transient Experiments

FIG. 9 depicts transients of (i) lithium ion insertion into a LiMn₂O₄carbon loaded electrode at 0.2 V vs. Ag/AgCl (“lithium extractionstep”), and lithium release at 1.2 V vs. Ag/AgCl in a 50 mM lithiumperchlorate aqueous solution (“lithium release/concentration step”).This experiment showed the capacity of the system to extract lithiumfrom an aqueous solution by insertion in the crystal structure of amanganese oxide lithium insertion compound deposited on a carbon felt,while release of lithium occurs in the dilute recovery solution.

Example 6 Electrochemical Plant to Extract Lithium from High AltitudeSalt Lakes

The battery-type lithium insertion electrode and chlorine reversibleelectrodes, “lithium extraction”/“lithium release/concentration” method,and electrochemical device design disclosed in the present applicationcan be applied to the large scale processing of brines from highaltitude lakes (e.g., salares from the Argentinian puna).

A clean energy source (e.g., solar, wind, geothermal or a combinationthereof) is used to power pumps that extract lithium-rich brine frombelow the lake surface. The electrochemical plant uses a plurality ofelectrochemical devices powered by the clean energy source to processthe brine and extract its lithium content. The lithium depleted brine issubsequently pumped below the lake surface. The resulting lithiumchloride can be further refined using the electrochemical devicesdisclosed in the instant application to yield high purity lithiumchloride, in a form with a purity greater than 99%. The purified lithiumchloride can in turn be electrolyzed directly by conventional methodsusing the electric power from the clean energy source to produce lithiummetal for a variety of purposes.

This extraction system is sustainable since it does not consume water byevaporation as in the present process used to extract lithium from saltlakes. Furthermore, the extraction system is faster that the presentlyused evaporation method (minutes-hours in the system and methodsdisclosed in the instant patent application versus months in theevaporation method). In addition, the disclosed system has a low energyimpact since the insertion (extraction) of lithium from the brine is aspontaneous process in a battery-type electrode, and the release oflithium and pumping of brine and electrolyte are low consuming energyprocesses that can be powers by renewable energy sources such as solarenergy.

Example 7 Use of a Polypyrrole/Carbon Chloride Reversible Electrode toCapture (or Release) Chloride Ions and a LiMn₂O₄/Carbon InsertionElectrode to Capture (or Release) Lithium

Polypyrrole is a conducting polymer that can be deposited onto thecarbon felt fibers either by chemical or electrochemical polymerizationof pyrrole from acid solutions. Upon oxidation polypyrrole uptake anionsin order to maintain neutrality of charges and conversely on reductionpolypyrrole releases the anion into solution. Thus, polypyrrole can beemployed as anode/cathode to capture/release selectively anions such aschloride from the electrolyte, in our case a brine, according to thereactions shown in FIG. 10. Accordingly, an extraction process wasdesigned in which the lithium intercalation cathode was acarbon-supported LiMn₂O₄ electrode, and the reversible chlorideelectrode capturing chloride ions simultaneously to the cathodicinsertion of lithium ions was a composite electrode comprisingpolypyrrole supported on carbon felt.

Polypyrrole electrodes offer several advantages over Ag/AgCl electrodes.Their cost is lower, they are easy to manufacture using chemicaloxidation of a pyrrole solution in contact with the carbon substrate(for example, a carbon felt), they do not release silver ions into theenvironment, and they have a large surface area.

General Description of the Lithium Extraction Process

A lithium extraction process was implement in which lithium chloride wasextracted from a sodium rich lithium brine (Li:Na 1:100) by enrichmentof a lithium chloride (LiCl) solution by successive electrochemicalinsertion in LiMn₂O₄ supported on carbon felt cathode in contact withthe brine, followed by release of LiCl from the electrode in a lithiumfree KCl electrolyte solution. Carbon felt-based electrodes were used.Carbon felt is conductive and presents a very high surface area tosupport the catalyst oxide for lithium insertion, LiMn₂O₄.

Since the lithium extraction selectivity with respect to sodium dependedon the Li to Na concentration ratio, successive electrochemical steps ofinsertion and release were need to selectively extract lithium.

The lithium insertion electrode (positive cathode) comprised a mixedlithium manganese oxide which in its reduced state had tri andtetravalent manganese ions in the crystal lattice, i.e., Mn^(III) andMn^(IV) and Li⁺ inserted in the crystal compensates the lower electricalcharge of Mn^(III). The insertion process occurred spontaneously as in abattery.

The second electrode (negative anode) captured chloride ions tocompensate the charge of polypyrrole in its reduced neutral statePP^(o), which underwent simultaneous oxidation to the [PP⁺Cl⁻] state.

During the release of LiCl in the lithium free electrolyte, the reverseprocess occurred at the electrodes with the opposite polarity, i.e., themanganese oxide was the negative electrode (anode) and the polypyrroleelectrode was the positive electrode (cathode). This process was notspontaneous and required the supply of energy to the electrochemicalcell.

During the lithium chloride recovery step, lithium ions were selectivelyinserted at the cathode and chloride ions at the anode, while during therelease of lithium chloride into the lithium free electrolyte, theopposite reaction occurred:

At each electrode the electrochemical processes were, at the cathode:

and at the reduced neutral polypyrrole anode:

It was possible to calculate the capacity of LiMn₂O₄ since 181 grams ofthe compound contain 7 grams of lithium. Therefore, a full insertion canproduce a theoretical maximum of 39 mg of lithium per gram of manganeseoxide. In the case of LiFePO₄ 158 grams of the compound can insert 7grams of lithium, and therefore can produce a theoretical maximum of44.3 mg of lithium per gram of iron phosphate.

The previously shown FIG. 6 a cyclic voltammetry of lithiuminsertion/release at a carbon supported LiMn₂O₄ electrode. The electrodepotential was indicated with respect to a Ag/AgCl reference electrodeand also in the Li/Li+ scale. In the cathodic extreme lithium wasinserted into the manganese oxide lattice, while at positive potentialsrelease of lithium ions from the oxide to the solution occurred. SeeCairns et al. Journal of The Electrochemical Society 146: 4339-4347(1999). Since the electrode potential is a measure of the degree oflithium insertion in the oxide (see, Tarascon & Guyomard, J.Electrochem. Soc. 138: 2864 (1991)), the electrode potential wasmonitored during insertion and release of lithium from brines.

Electrodes

Conductive carbon felt electrodes (National Electric Carbon Products, adivision of Morgan Specialty Graphite, Greenville, S.C., USA) were cutin 50×50 mm pieces, supported in TEFLON® holders, and immersed in 180 mLof electrolyte (brine or recovery solution). The photographs in FIG. 11depict the experimental setup.

A TEFLON® frame held the carbon felt electrodes separated by a TEFLON®net to avoid short circuit. Each electrode was connected via a goldplate to the leads of the potentiostat. No membrane such as NAFION™ wasemployed in this experimental setup.

Carbon felt samples (50×50 mm) were cleaned with isopropanol during 5minutes and then pre-treated with dilute sulfuric acid for 10 minuteswith sonication. LiMn₂O₄ electrodes were prepared by impregnating thecarbon felt pieces with a slurry made of 2.4 g LiMn₂O₄. 0.3 g SHAWINIGANBLACK® carbon, and 0.3 g PVC binder suspended in 5 mL ofN-methylpyrrolidone, and dried at 70° C. for 12 hours. FIG. 12 shows SEMmicrographs of the resulting carbon fibers in the felt covered byLiMn₂O₄ crystals. Good coverage of the carbon fibers by the LiMn₂O₄crystals was observed.

Polypyrrole electrodes were obtained by chemical polymerization ofpyrrole as follows: Carbon felt samples were sequentially immersed in0.5 M pyrrole in 0.02 M hydrochloric acid (solution A) and 0.5 Mammonium persulfate (solution B), for 5 minutes in each solution. Afterrinsing with distilled water, the felts were dried at 105° C. for 24hours. FIG. 13 is an SEM micrograph depicting the polypyrrole deposit onthe carbon felts.

Two electrochemical treatments were employed for the capture of lithiumchloride from the brine and for the release of the captured lithium intoa lithium free solution as follows:

-   -   a. For capturing lithium at the cathode and chloride at the        anode, a galvanostatic method was used. −25 mA of constant DC        current was applied to a 25 cm² geometric area of the        three-dimensional porous carbon felt electrodes, following the        electrode potential as a function of time. The electrolysis        charge was given by the current times the elapsed time,        typically 7200 seconds (2 hours) or 180 coulombs.    -   b. For the release of LiCl into a lithium free solution        containing dilute potassium chloride, or eventually containing        dilute lithium chloride, a potentiostatic treatment under        stirring was employed as follows. The LiMn₂O₄/carbon electrode        was polarized at 1.4 V vs. Ag/AgCl; 3 M NaCl reference        electrode, and oxidation of Mn^(III) released the inserted        lithium. The current transient was followed. On the other        electrode (negative) the release of chloride occurred as        oxidized polypyrrole was reduced.        Extraction of Lithium from Natural Brines

The capacity of the disclosed method and device to extract selectivelylithium from a natural brine was tested using brine samples of theOllaroz salt lake in the province of Jujuy (Argentina), with contained aLi:Na concentration ratio of 1:100. In addition to lithium, the brinesamples contained sodium, potassium, magnesium, boron, etc. The chemicalanalysis by atomic emission of the brine showed, among other components,Li: 1.3 g/L; Na: 62.6 g/L; Ca: 3.6 g/L; Mg: 3.3 g/L; K: 8.1 g/L.

1. Insertion of LiCl from Natural Brine

Lithium ions were inserted in the LiMn₂O₄/carbon felt cathode andchloride ions where inserted in the polypyrrole/carbon felt anode from abrine solution (180 mL) with a 1:100 lithium to sodium initialconcentration ratio using galvanostatic electrochemical insertion. Theelectrode Geometric Area was 25 cm² and the load was 0.6 g of LiMn₂O₄.When a constant current of −25 mA was applied to the electrochemicalreactor, the cathode potential with respect to a Ag/AgCl; 3 M NaClreference electrode (approx. 3 V vs. Li/Li⁺) evolved with time duringlithium insertion. Total charge was 180 coulomb.

FIG. 14 shows four transients corresponding to four lithium chloridecapture steps. The electrode potential depended on the lithiumconcentration in solution according to the Nernst equation. In the firstextraction the brine solution was highly concentrated in lithium, whilethe subsequent lithium recovery solutions were very dilute (in themillimolar range). The total electrical charge passed was −180 coulombs(−25 mA×7200 seconds). If all the charge was due to lithium insertion,then 13 mg of lithium should have been extracted.

2. Rinsing the Felts

Electrodes were rinsed with distilled water by immersion in a series ofwater baths under stirring until the sodium concentration in the washingliquid was less than 1 ppm.

3. Lithium Release

The release of lithium can be achieved by passing a constant current(galvanostatic pulse) or by applying a constant potential in the regionwhere Mn^(III) is oxidized to Mn^(IV) as shown in the cyclic voltammetryabove. The potentiostatic transient is preferred to avoid reachingexcessive oxidant potential when lithium is depleted in the brine orrecovery electrolyte.

In the lithium release process, the polarity of the electrodes wasreversed in an electrolyte solution containing no lithium but containingdilute KCl as a background electrolyte to provide enough conductivity.The potentiostatic electrochemical release of lithium ions from theLiMn₂O₄/carbon felt anode and the release of chloride from thepolypyrrole/carbon felt cathode took place in a lithium free 0.05 M KClsolution under potential control at 1.4 V during 7200 seconds with atotal charge of 22.18 Coulombs. The electrolyte was stirred to avoidconcentration polarization of lithium ions at the electrode surface.FIG. 15 shows the current transients for a sequence of lithium recoverysteps during which lithium was released from the LiMn₂O₄ electrode.Alternatively, in some experiments (not shown) a dilute lithium chloridesolution was used, which was then enriched in lithium during theprocess.

The electrolyte was analyzed for lithium and sodium yield. Theenrichments process yielded 1.9 mg (1.5 mM) of lithium and 3.9 mg (0.94mM) of sodium. Therefore the first electrochemical insertion extractionstep achieved a Li:Na atomic ratio of 1.59 from 0.01 in the initialbrine. The sodium retained at the electrode could have beenelectrostatically adsorbed onto the large area of oxide and carbon feltand also co-inserted into the LiMn₂O₄ nanoparticles. Since thecrystallographic ionic radius of the sodium ion (9.8 nm) or potassium(13.6 nm), is larger that of lithium ion (6.8 nm), less sodium orpotassium can insert into the spinel oxide lattice.

The resulting liquid from the first extraction (with a Li:Na atomicratio of 1.59) was subjected to a second extraction process with aLiMn₂O₄/carbon felt cathode and a reduced polypyrrole anode afterthoroughly rinsing the electrodes employed in the first step. Thegalvanostatic potential-time transient showed a similar shape as the oneobtained in the first electrochemical extraction step. The release ofLiCl in a lithium free KCl dilute solution took place underpotentio-static control at 1.4 V (reversing the electrodes polarity)during the same time, 7200 seconds. FIG. 16 shows the evolution of theelectrical charge during the release of lithium ions from theLiMn2O4/carbon electrode into the electrolyte.

As shown in TABLE 1, increasing the number of extraction/release stepsincreased the selectivity of lithium with respect to sodium from aninitial Li:Na concentration ratio of 1:100 to a final Li:Naconcentration ratio of 12.4:1 after three cycles.

TABLE 1 Results from increasing the number of extraction and releasesteps to increase lithium selectivity. Extraction [Li

] ppm Li [Na

] Ppm Na [Li]/[Na] 0.01 1st. 1.5 1.9 0.94 3.9 1.59 2nd. 2.3 2.9 1.08 4.52.30 3rd. 3.5 4.9 0.31 1.3 12.4

indicates data missing or illegible when filed

Example 8 Alternative Electrodes and Electrochemical Device

In this alternative method, particles of carbon (calcined coke frompetroleum) with a diameter in the 200-800 micrometer range were loadedwith either LiMn₂O₄ or polypyrrol and placed in a thin packed bedbetween a titanium current collector and a polyester gauze. Thisarrangement allowed the electrolyte to flow axially at a considerableflow rate (i.e., 2 to 30 mL per second) while keeping good electricalcontact among the coke particles, and among the coke particles and thecurrent collector. The reactor assembly had no separating membranebetween the cathodic and anodic compartments.

Achieving high electrolyte flow with low pressure drop, good particle toparticle electrical contact, and low ohmic drop at the lowestelectrolyte concentrations is important in electrochemical reactordesign. The use of coke particles several hundred micrometers in sizegave (i) a larger surface area of contact between the electrode materialsupported on carbon particles and the electrolyte and (ii) a goodflowbed as compared to the use of only carbon felts as described in theprevious Example.

In a typical preparation of the lithium extracting electrode material,60 g of 500 micrometer size coke particles were mixed with 13 g ofLiMn₂O₄, 2.75 g of polyvinylidene fluoride (PVDF), and 2.75 g of VULCAN®carbon black. This mixture was dispersed in pyrrolydone, thoroughlystirred during 24 hours, and dried in a vacuum oven at 70° C. for 24hours. The resulting powder was compressed between the carbon felt andthe polyester gauze.

For the chloride extracting electrode material, 60 g of 500 micrometersize coke particles were dispersed in a solution containing 0.5 Mpyrrole. 0.02 hydrochloric acid and a solution of 0.5 M ammoniumpersulfate. After evaporation at 110° C. for 24 hours, the cokeparticles loaded with polypyrrole were washed with distilled water,dried, and compressed between the carbon felt and the polyester gauze ofthe second electrode. A typical SEM micrograph of coke particles loadedwith LiMn₂O₄ crystals is shown in FIG. 17.

The functionalized coke electrode particles were used to assemble aPress Filter reactor (type FM100) with axial flux of electrolyte andperpendicular current flow as shown in FIG. 18. The reactor consisted of(i) titanium current collectors, (ii) carbon felt support and petroleumcalcined coke carbon support of LiMn₂O₄ at one electrode, (iii) carbonfelt support and polypyrrole at the other electrode, (iv) a TEFLON®framework, and (v) a polyester gauze in undivided cells. In order toincrease the production of lithium, several undivided cells were stackedand connected in series in a FM100 type reactor. The same current wascirculated through all the cells in series, while a potential differencebetween the anode and cathode of each cell (typically 1.2 v) wasapplied.

The charge and discharge transients showed that the capture and releaseof lithium ions by LiMn₂O₄ was reversible (see FIG. 19).

Theoretically, each 7 g of lithium extracted from brine would require anelectrical charge of 26.8 A.h (96,500 coulombs/3600 s.h⁻¹). To extract 7g of Li⁺, 126 g of LiMn₂O₄ or 174 g of MnO₂ would be needed. Since theconcentration of lithium in brines of the Argentinian Puna (for example,brines from the Ollaroz Saltpan) is approximately 1 g per liter, 7liters of brine would yield a theoretical maximum of 7 g of lithium.

In the first cycle, the LiMn₂O₄ electrode was delithiated to produce thelithium ion insertion oxide electrode material, which spontaneouslyextracted lithium ions when contacted with lithium containing brines.The discharge and charge curves at constant current (±0.5 mA/cm²) during2 hours are shown in FIG. 20. FIG. 21 shows a plot of potential-charge.Integration of the potential-charge curve indicated that the energybalance per ton of lithium extracted was 200 kWh.

The functionalized coke electrode particles were also used to assemblean alternative type of reactor. A packed bed reactor with both LiMn₂O₄and polypyrrol supported on coke carbon was assembled according to theconfiguration showed in FIG. 22. This configuration provided proof ofconcept for a practical three dimensional reactor at the laboratoryscale with coke compact bed electrodes loaded respectively with LiMn₂O₄and polypyrrole. The electrolyte flow and current flow werelongitudinal. The system presented large ohmic drops at the packed bedflooded with electrolyte but very small pressure drops.

The longitudinally packed bed cylindrical reactor prototype consisted ofa glass cylinder with two compartments separated by porous frittedglass, titanium mesh current collectors with titanium rod electricalconnectors, two packed beds containing 20 g of coke loaded withelectrode materials, rubber stoppers, and tubing connecting to a pistonflow pump (see FIG. 23 and TABLE 2). By connecting a mercury pressuremeter, the pressure drop in the reactor was measured at different flowrates (0-30 mL per second) as shown in FIG. 24.

TABLE 2 Characteristics of packed bed cylindrical reactor prototype.Mass of coke particles 20 g Packed Bed Height 4 cm Reactor diameter 4 cmReactor cross section 12.57 cm² Pack bed volume 50.27 cm³ Coke density2,0075 g/cm³ Pososity 80.85%

Considering (i) solar panels having a cost of $2,000 per kW, (ii) apower consumption of 200 kWh per ton of lithium extracted, and (iii) asolar energy production of 50 kW in one day, one ton of lithium could berecovered per day with a capital investment of $100,000 dollars (800square meters of solar panels, which have a life time of 30 years).During the 30 year lifetime of the solar panels, this solar-poweredelectrochemical production system could yield 11,000 tons of lithium.Accordingly, the cost of the production using the electrochemicalextraction method disclosed herein would be approximately $10 per ton oflithium (plus the cost of energy for pumping brine and other engineeringoperations as well as energy losses due to kinetics, etc.). This systemcould be used to recover lithium from aqueous solutions, including saltlake brines, sea water, geothermal water, and oil salt water. Inaddition to its low monetary cost, the process is highly advantageoussince (i) it is clean, not consuming water, lime or Solvay, (ii) it hasa low energy cost, c.a. 200 kWh/ton, (iii) it is selective for lithiumwith respect to sodium if applied in repeated cycles, and (iv) itproduces high purity lithium chloride suitable for battery use.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the present invention ascontemplated by the inventor(s), and thus, are not intended to limit thepresent invention and the appended claims in any way.

The present invention has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent invention. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

1. A packed bed electrochemical cell for extracting lithium from anaqueous solution containing lithium ions comprising: (a) a firstelectrode comprising a compartment packed with a high surface carbonsubstrate coated with a lithium insertion compound comprising LiMn₂O₄,(b) a second electrode comprising a compartment packed with a highsurface carbon substrate coated with a chloride reversible electrodematerial; and (c) a non-membranous porous material interposed betweenthe first and second electrode, wherein the high surface carbonsubstrate comprises calcined coke carbon particles.
 2. The packed bedelectrochemical cell according to claim 1, wherein the calcined cokecarbon particles are calcined petroleum coke carbon particles.
 3. Thepacked bed electrochemical cell according to claim 1, wherein thechloride reversible electrode material comprises polypyrrole.
 4. Thepacked bed electrochemical cell according to claim 1, wherein thenon-membranous porous material separating the first and second electrodecomprises a porous fritted glass separator.
 5. The packed bedelectrochemical cell according to claim 1, further comprising currentcollection contacts which are in contact with the electrodes.
 6. Thepacked bed electrochemical cell according to claim 5, where the currentcollection contacts are titanium mesh current collectors. 7-32.(canceled)
 33. An electrochemical device for extracting lithium from anaqueous solution containing lithium ions comprising at least onebattery-type electrode comprising a porous or high surface substratecoated with a lithium insertion compound, wherein said device does notcomprise a counter-electrode.
 34. The electrochemical device accordingto claim 33, wherein the device further comprises a chloride orpolypyrrole reversible electrode.
 35. The electrochemical deviceaccording to claim 33, wherein the substrate is a carbon substrate. 36.The electrochemical device according to claim 35, wherein the carbonsubstrate is a conductive substrate.
 37. The electrochemical deviceaccording to claim 33, wherein the battery-type electrode comprises aconductive additive material.
 38. The electrochemical device accordingto claim 37, wherein the conductive additive material is carbon black.39. The electrochemical device according to claim 33, wherein thelithium insertion compound comprises a manganese oxide.
 40. Theelectrochemical device according to claim 39, wherein the manganeseoxide comprises γ-MnO₂ and/or λ-MnO₂.
 41. The electrochemical deviceaccording to claim 39, wherein the manganese oxide has a spinel crystalstructure.
 42. The electrochemical device according to claim 39, whereinthe manganese oxide comprises LiMn₂O₄.
 43. The electrochemical deviceaccording to claim 33, wherein the lithium insertion compound compriseslithium cobalt oxide, lithium iron phosphate, lithium manganese oxide,or combinations thereof.
 44. The electrochemical device according toclaim 43, wherein the lithium cobalt oxide comprises LiCoO₂.
 45. Theelectrochemical device according to claim 43, wherein the lithium ironphosphate comprises LiFePO₄.
 46. The electrochemical device according toclaim 33, wherein the battery-type electrode is prepared byelectrolytical delithiation of a porous or high surface substrate coatedwith lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄),lithium manganese oxide (LiMn₂O₄), or combinations thereof.
 47. Theelectrochemical device according to claim 33, wherein the carbonsubstrate is selected from the group consisting of carbon felt, carboncloth, carbon paper, graphite granules, granite foam, high surface areagraphite fiber, and combinations thereof.
 48. The electrochemical deviceaccording to claim 33, wherein the carbon substrate is a carbon felt.49. The electrochemical device according to claim 34, wherein thechloride reversible electrode comprises a porous or high surface carbonsubstrate and silver metal particles.
 50. The electrochemical deviceaccording to claim 49, wherein the silver metal particles arenanoparticles.
 51. The electrochemical device according to claim 34,wherein the chloride reversible electrode further comprises anelectrically conductive polymer.
 52. The electrochemical deviceaccording to claim 51, wherein the electrically conductive polymer is apolypyrrole.
 53. The electrochemical device according to claim 33,wherein the lithium ions in the aqueous solution are captured byinsertion in the crystal structure of the battery-type electrode. 54.The electrochemical device according to claim 34, wherein thebattery-type electrode and chloride reversible electrode are positionedin separate half-cells.
 55. The electrochemical device according toclaim 54, wherein the half-cell comprising the battery-type electrodeand the half-cell comprising the chloride reversible electrode areseparated by a semi-permeable electrolysis membrane.
 56. Theelectrochemical device according to claim 55, wherein the electrolysismembrane is an ionomer membrane.
 57. The electrochemical deviceaccording to claim 56, wherein the ionomer membrane is a NAFION®membrane.
 58. The electrochemical device according to claim 57, whereinthe NAFION® membrane is NAFION®
 324. 59-67. (canceled)